SUMMARY Projects 1 and 2 will require high-end optical microscopy with single molecule tracking and single vesicle fusion and FRET capabilities to achieve aims 1 and 2, and 1 and 3, respectively. Project 3 will measure interbilayer distances by FLIC microscopy (aim 1) and determine synaptotagmin-induced changes in lipid order by ATR-FTIR spectroscopy (aim 3). Core A will provide the necessary state-of-the-art instrumentation, technical know-how, and personnel training to realize these aims of all three Projects. In addition, the Core will train users, provide customable software tools, and assist with image and data analysis.